forked from AuroraMiddleware/gtk
cb918cdb02
2004-11-12 Matthias Clasen <mclasen@redhat.com> Changes to make gdk-pixbuf threadsafe (#157310, #157306, Colin Walters): * gdk-pixbuf-io.h (enum GdkPixbufFormatFlags): Add GDK_PIXBUF_FORMAT_THREADSAFE to indicate that an image loader is threadsafe. * gdk-pixbuf-io.c (get_file_formats, _gdk_pixbuf_load_module): Use a lock to make initialization of global data structures threadsafe. * gdk-pixbuf-private.h: * gdk-pixbuf-io.c (_gdk_pixbuf_lock, _gdk_pixbuf_unlock): Auxiliary functions which use another lock to protect threadunsafe image loaders. * gdk-pixbuf-io.c (gdk_pixbuf_real_save): (save_to_callback_with_tmp_file): (gdk_pixbuf_real_save_to_callback): (gdk_pixbuf_new_from_xpm_data): (_gdk_pixbuf_generic_image_load): * gdk-pixbuf-animation.c (gdk_pixbuf_animation_new_from_file): * gdk-pixbuf-loader.c (gdk_pixbuf_loader_load_module): (gdk_pixbuf_loader_close): (gdk_pixbuf_loader_finalize): Use _gdk_pixbuf_lock() and _gdk_pixbuf_unlock(). * io-ani.c, io-bmp.c, io-gif.c, io-ico.c: * io-jpeg.c, io-pcx.c, io-png.c, io-pnm.c: * io-ras.c, io-tga.c, io-wbmp.c, io-xbm.c: * io-xpm.c: Mark as threadsafe. * io-tiff.c: Remove pointless locking, mark as threadunsafe.
371 lines
11 KiB
Plaintext
371 lines
11 KiB
Plaintext
<!-- ##### SECTION Title ##### -->
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Module Interface
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<!-- ##### SECTION Short_Description ##### -->
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Extending &gdk-pixbuf;
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<!-- ##### SECTION Long_Description ##### -->
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<para>
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If &gdk-pixbuf; has been compiled with GModule support, it can be extended by
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modules which can load (and perhaps also save) new image and animation
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formats. Each loadable module must export a
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#GdkPixbufModuleFillInfoFunc function named <function>fill_info</function> and
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a #GdkPixbufModuleFillVtableFunc function named
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<function>fill_vtable</function>.
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</para>
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<para>
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In order to make format-checking work before actually loading the modules
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(which may require dlopening image libraries), modules export their
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signatures (and other information) via the <function>fill_info</function>
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function. An external utility, <command>gdk-pixbuf-query-loaders</command>,
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uses this to create a text file containing a list of all available loaders and
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their signatures. This file is then read at runtime by &gdk-pixbuf; to obtain
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the list of available loaders and their signatures.
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</para>
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<para>
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Modules may only implement a subset of the functionality available via
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#GdkPixbufModule. If a particular functionality is not implemented, the
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<function>fill_vtable</function> function will simply not set the corresponding
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function pointers of the #GdkPixbufModule structure. If a module supports
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incremental loading (i.e. provides #begin_load, #stop_load and
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#load_increment), it doesn't have to implement #load, since &gdk-pixbuf; can
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supply a generic #load implementation wrapping the incremental loading.
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</para>
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<para>
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Installing a module is a two-step process:
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<itemizedlist>
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<listitem><para>copy the module file(s) to the loader directory (normally
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<filename><replaceable>libdir</replaceable>/gtk-2.0/<replaceable>version</replaceable>/loaders</filename>,
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unless overridden by the environment variable
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<envar>GDK_PIXBUF_MODULEDIR</envar>)
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</para></listitem>
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<listitem><para>call <command>gdk-pixbuf-query-loaders</command> to update the
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module file (normally
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<filename><replaceable>sysconfdir</replaceable>/gtk-2.0/gdk-pixbuf.loaders</filename>,
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unless overridden by the environment variable
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<envar>GDK_PIXBUF_MODULE_FILE</envar>)
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</para></listitem>
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</itemizedlist>
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</para>
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<para>
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The &gdk-pixbuf; interfaces needed for implementing modules are contained in
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<filename>gdk-pixbuf-io.h</filename> (and
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<filename>gdk-pixbuf-animation.h</filename> if the module supports animations).
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They are not covered by the same stability guarantees as the regular
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&gdk-pixbuf; API. To underline this fact, they are protected by
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<literal>#ifdef GDK_PIXBUF_ENABLE_BACKEND</literal>.
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</para>
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<!-- ##### SECTION See_Also ##### -->
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<para>
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</para>
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<!-- ##### FUNCTION gdk_pixbuf_set_option ##### -->
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<para>
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</para>
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@pixbuf:
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@key:
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@value:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_get_formats ##### -->
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<para>
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</para>
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_get_name ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_get_description ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_get_mime_types ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_get_extensions ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_is_writable ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_is_scalable ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_is_disabled ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### FUNCTION gdk_pixbuf_format_set_disabled ##### -->
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<para>
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</para>
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@format:
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@disabled:
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<!-- ##### FUNCTION gdk_pixbuf_format_get_license ##### -->
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<para>
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</para>
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@format:
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@Returns:
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<!-- ##### STRUCT GdkPixbufFormat ##### -->
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<para>
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A #GdkPixbufFormat contains information about the image format accepted by a
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module. Only modules should access the fields directly, applications should
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use the <function>gdk_pixbuf_format_*</function> functions.
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</para>
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@name: the name of the image format.
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@signature: the signature of the module.
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@domain: the message domain for the @description.
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@description: a description of the image format.
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@mime_types: a %NULL-terminated array of MIME types for the image format.
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@extensions: a %NULL-terminated array of typical filename extensions for the
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image format.
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@flags: a combination of #GdkPixbufFormatFlags.
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@disabled: a boolean determining whether the loader is disabled.
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@license: a string containing license information, typically set to
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shorthands like "GPL", "LGPL", etc.
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@Since: 2.2
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<!-- ##### ENUM GdkPixbufFormatFlags ##### -->
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<para>
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Flags which allow a module to specify further details about the supported
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operations.
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</para>
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@GDK_PIXBUF_FORMAT_WRITABLE: the module can write out images in the format.
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@GDK_PIXBUF_FORMAT_SCALABLE: the image format is scalable
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@GDK_PIXBUF_FORMAT_THREADSAFE: the module is threadsafe. If this flag is not
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set, &gdk-pixbuf; will use a lock to prevent multiple threads from using
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this module at the same time. (Since 2.6)
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@Since: 2.2
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<!-- ##### STRUCT GdkPixbufModulePattern ##### -->
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<para>
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The signature of a module is a set of prefixes. Prefixes are encoded as
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pairs of ordinary strings, where the second string, if not %NULL, must be
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of the same length as the first one and may contain ' ', '!', 'x', 'z',
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and 'n' to indicate bytes that must be matched, not matched,
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"don't-care"-bytes, zeros and non-zeros.
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Each prefix has an associated integer that describes the relevance of
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the prefix, with 0 meaning a mismatch and 100 a "perfect match".
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</para>
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<para>
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The signature of a module is stored as an array of
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#GdkPixbufModulePattern<!-- -->s. The array is terminated by a pattern
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where the @prefix is %NULL.
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</para>
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<informalexample><programlisting>
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GdkPixbufModulePattern *signature[] = {
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{ "abcdx", " !x z", 100 },
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{ "bla", NULL, 90 },
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{ NULL, NULL, 0 }
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};
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</programlisting>
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The example matches e.g. "auud\0" with relevance 100, and "blau" with
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relevance 90.</informalexample>
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@prefix: the prefix for this pattern
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@mask: mask containing bytes which modify how the prefix is matched against
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test data
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@relevance: relevance of this pattern
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@Since: 2.2
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<!-- ##### USER_FUNCTION GdkPixbufModuleFillVtableFunc ##### -->
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<para>
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Defines the type of the function used to set the vtable of a
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#GdkPixbufModule when it is loaded.
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</para>
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@module: a #GdkPixbufModule.
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@Since: 2.2
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<!-- ##### USER_FUNCTION GdkPixbufModuleFillInfoFunc ##### -->
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<para>
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Defines the type of the function used to fill a
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#GdkPixbufFormat structure with information about a module.
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</para>
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@info: a #GdkPixbufFormat.
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@Since: 2.2
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<!-- ##### USER_FUNCTION GdkPixbufModuleSizeFunc ##### -->
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<para>
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Defines the type of the function that gets called once the size
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of the loaded image is known.
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</para>
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<para>
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The function is expected to set @width and @height to the desired
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size to which the image should be scaled. If a module has no efficient
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way to achieve the desired scaling during the loading of the image, it may
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either ignore the size request, or only approximate it -- &gdk-pixbuf; will
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then perform the required scaling on the completely loaded image.
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</para>
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<para>
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If the function sets @width or @height to zero, the module should interpret
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this as a hint that it will be closed soon and shouldn't allocate further
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resources. This convention is used to implement gdk_pixbuf_get_file_info()
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efficiently.
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</para>
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@width: pointer to a location containing the current image width
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@height: pointer to a location containing the current image height
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@user_data: the loader.
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@Since: 2.2
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<!-- ##### USER_FUNCTION GdkPixbufModulePreparedFunc ##### -->
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<para>
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Defines the type of the function that gets called once the initial
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setup of @pixbuf is done.
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</para>
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<para>
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#GdkPixbufLoader uses a function of this type to emit the
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"<link linkend="GdkPixbufLoader-area-prepared">area_prepared</link>"
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signal.
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</para>
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@pixbuf: the #GdkPixbuf that is currently being loaded.
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@anim: if an animation is being loaded, the #GdkPixbufAnimation, else %NULL.
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@user_data: the loader.
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@Since: 2.2
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<!-- ##### USER_FUNCTION GdkPixbufModuleUpdatedFunc ##### -->
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<para>
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Defines the type of the function that gets called every time a region
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of @pixbuf is updated.
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</para>
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<para>
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#GdkPixbufLoader uses a function of this type to emit the
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"<link linkend="GdkPixbufLoader-area-updated">area_updated</link>"
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signal.
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</para>
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@pixbuf: the #GdkPixbuf that is currently being loaded.
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@x: the X origin of the updated area.
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@y: the Y origin of the updated area.
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@width: the width of the updated area.
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@height: the height of the updated area.
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@user_data: the loader.
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@Since: 2.2
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<!-- ##### STRUCT GdkPixbufModule ##### -->
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<para>
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A #GdkPixbufModule contains the necessary functions to load and save
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images in a certain file format.
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</para>
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<para>
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A #GdkPixbufModule can be loaded dynamically from a #GModule.
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Each loadable module must contain a #GdkPixbufModuleFillVtableFunc function
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named <function>fill_vtable</function>, which will get called when the module
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is loaded and must set the function pointers of the #GdkPixbufModule.
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</para>
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@module_name: the name of the module, usually the same as the
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usual file extension for images of this type, eg. "xpm", "jpeg" or "png".
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@module_path: the path from which the module is loaded.
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@module: the loaded #GModule.
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@info: a #GdkPixbufFormat holding information about the module.
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@load: loads an image from a file.
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@load_xpm_data: loads an image from data in memory.
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@begin_load: begins an incremental load.
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@stop_load: stops an incremental load.
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@load_increment: continues an incremental load.
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@load_animation: loads an animation from a file.
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@save: saves a #GdkPixbuf to a file.
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@save_to_callback:
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<!-- ##### STRUCT GdkPixbufAnimationClass ##### -->
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<para>
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Modules supporting animations must derive a type from
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#GdkPixbufAnimation, providing suitable implementations of the
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virtual functions.
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</para>
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@parent_class:
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@is_static_image: returns whether the given animation is just a static image.
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@get_static_image: returns a static image representing the given animation.
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@get_size: fills @width and @height with the frame size of the animation.
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@get_iter: returns an iterator for the given animation.
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<!-- ##### STRUCT GdkPixbufAnimationIterClass ##### -->
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<para>
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Modules supporting animations must derive a type from
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#GdkPixbufAnimationIter, providing suitable implementations of the
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virtual functions.
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</para>
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@parent_class:
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@get_delay_time: returns the time in milliseconds that the current frame
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should be shown.
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@get_pixbuf: returns the current frame.
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@on_currently_loading_frame: returns whether the current frame of @iter is
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being loaded.
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@advance: advances the iterator to @current_time, possibly changing the
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current frame.
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